Graphene-Based Nanocomposites

Abstract

Since the historical observation of single layer graphene by Germ and his co-workers in 2004, this atomically thin carbon film has received ever-increasing attention and become a rapidly rising star on the horizon of materials science and condensed-matter physics (Novoselov et al., 2004). Graphene exhibits many unusual and useful properties such as a large theoretical specific surface area (2630 m2 g-1) (Stoller et al., 2008), high values of Young’s modulus (~1.1 Tpa), excellent thermal conductivity (~5000 W m-1 s-1) (Park & Ruoff, 2009), and amazing intrinsic mobility (200 000 cm2 v-1 s-1). Moreover, the extraordinary transport phenomena of graphene have also been well documented, including massless Dirac fermions (Novoselov et al., 2005), ambipolar field effect (Novoselov et al., 2004 ), room-temperature quantum Hall effect (Zhang et al., 2005), etc. These fascinating performances have attracted extensive concern in recent years with ever-increasing scientific and technological impetus. Among the numerous methods for harnessing these peculiar properties, one possible route would be to incorporate graphene sheets into composite materials (Stankovich et al., 2006). The easy synthesis, low cost and non-toxicity of graphene make this material a promising candidate for many technological applications (Geim & Novoselov, 2007; Allen et al., 2010). For example, graphene sheets are excellent nanoscale substrates for the formation of silver-nanoparticle films. These silver-nanoparticle films assembled on the single-layer sheets are flexible and can form stable suspensions in aqueous solutions (Xu et al., 2009). They can be processed facilely into paper-like materials and flexible electronic materials to satisfy different requirements for many products, such as membranes, anisotropic conductors, biological sensors and optoelectronic nano-devices, etc. Graphene sheets and exfoliated graphene oxide possess large surface areas and thus may be excellent support materials to disperse and stabilize inorganic nanoparticles, such as Pt, Co3O4, CuO, MnO2, MnOOH, Co(OH)2, etc., effectively inhibiting the aggregation in postsynthesis and thereby giving a relatively higher utilization of the active material. Decoration of graphene sheets with nanoparticles has been demonstrated to reveal special features in new hybrids that can be widely utilized in catalysts, supercapacitors, Li-ion batteries, etc. It was found that the introduction of less amount of graphene oxide into PANI could induce a synergistic effect, greatly enhancing the electrochemical performance of PANI as a supercapacitor electrode material (Wang et al., 2009a). The intent of this chapter is to provide a basic overview of graphene-based nanocomposites. The emphasis is primarily on the different synthetic strategies that have been pursued so far